Chapter 3

Concepts of Database Management
Seventh Edition
Chapter 3
The Relational Model 2: SQL
Objectives
•
•
•
•
•
Introduce Structured Query Language (SQL)
Use simple and compound conditions in SQL
Use computed fields in SQL
Use built-in SQL functions
Use subqueries in SQL
2
Objectives (continued)
•
•
•
•
•
Group records in SQL
Join tables using SQL
Perform union operations in SQL
Use SQL to update database data
Use an SQL query to create a table in a database
3
Introduction
• SQL (Structured Query Language)
– Allows users to query a relational database
– Must enter commands to obtain the desired results
– Standard language for relational database
manipulation
4
Getting Started with SQL
• If you are completing the work in this chapter using
Microsoft Office Access 2007, Microsoft Office
Access 2010, or MySQL version 4.1 or higher, the
following sections contain specific information
about your DBMS
5
Getting Started with Microsoft Office
Access 2007 and 2010
• If you are using the Access 2007 or 2010 version of
the Premiere Products database provided with the
Data Files for this text:
– Tables in the database have already been created
– You will not need to execute the CREATE TABLE
commands to create the tables or the INSERT
commands to add records to the tables
6
Getting Started with Microsoft Office
Access 2007 and 2010 (continued)
• To execute SQL commands shown in the figures in
Access 2007 or Access 2010:
–
–
–
–
–
Open the Premiere Products database
Click the Create tab on the Ribbon
Click the Query Design button in the Other group
Click the Close button in the Show Table dialog box
Click the View button arrow in the Results group on
the Query Design Tools tab, then click SQL View
– The Query1 tab displays the query in SQL view,
ready for you to type your SQL commands
7
Getting Started with MySQL
• MySQL-Premiere script provided with the Data
Files for this text will:
– Activate the database
– Create the tables
– Insert the records
• To run a script in MySQL:
– Type the SOURCE command followed by the name
of the file
– Press the Enter key
8
Getting Started with MySQL
(continued)
• Before typing commands in MySQL, you must
activate the database by typing the USE command
followed by the name of the database
• The most recent command entered in MySQL is
stored in a special area of memory called the
statement history
9
Table Creation
• SQL CREATE TABLE command
– Creates a table by describing its layout
• Typical restrictions placed on table and column
names by DBMS
– Names cannot exceed 18 characters
– Names must start with a letter
– Names can contain only letters, numbers, and
underscores (_)
– Names cannot contain spaces
10
Table Creation (continued)
• INTEGER
– Number without a decimal point
• SMALLINT
– Uses less space than INTEGER
• DECIMAL(p,q)
– P number of digits; q number of decimal places
• CHAR(n)
– Character string n places long
• DATE
– Dates in DD-MON-YYYY or MM/DD/YYYY form
11
Simple Retrieval
• SELECT-FROM-WHERE: SQL retrieval command
– SELECT clause: lists fields to display
– FROM clause: lists table or tables that contain data
to display in query results
– WHERE clause (optional): lists any conditions to be
applied to the data to retrieve
• Simple condition: field name, a comparison
operator, and either another field name or a value
12
Simple Retrieval (continued)
• Retrieving all fields and all records
– Syntax: SELECT * FROM <table>
– Example 1: SELECT * FROM Customer
– Example 2: SELECT * FROM Rep
• Retrieving specific field(s)
• Syntax: SELECT <field1>, <field2>,..<fieldn> FROM
<table>
• Example 1: SELECT Customername, City, State FROM
Customer
• Example 2: SELECT Repnum, Lastname, Firstname,
Commission, Rate FROM Rep
13
Non-Graded Exercise
1. Show all the fields and records from Rep table
2. Show all fields and records Part table
3. Show the Last name and First name of all Sales
Rep from Rep table
4. Show the Part number, Description, On Hand
Quantity and Price from Part table
14
Simple Retrieval – Filtering Records
• Filtering records to retrieve using WHERE clause
– Syntax: SELECT * FROM <table>
– Example 1: (Filtering records with a Text/String field)
SELECT * FROM Customer WHERE City=‘Grove’
– Example 2: (Filtering records with a Numeric field)
SELECT * FROM Customer WHERE CreditLimit=7500
– Example 3: (Filtering records using specific fields)
SELECT Customername, City WHERE City = ‘Grove’
– Example 4: (Filtering records using not equal)
SELECT * FROM City WHERE City <> ‘Fillmore’
– Note : If it is a string or a text the value should have
a quote like in ‘Grove’ but if it is numeric do not put a
quote.
15
Simple Retrieval (continued)
FIGURE 3-6: SQL query with WHERE condition
16
Simple Retrieval (continued)
FIGURE 3-7: Query results
17
Relational Operators
Operator
Description
Example
>
Greater Than
Age>20
<
Less than
Age<21
=
Equal
City=‘Grove’
>=
Greater than or Equal
CreditLimit >= 10000
<=
Less than or Equal
Balance<=5000
<>
Not Equal
City <> ‘Grove’
Date Comparisons
Database
Example
MS Access
OrderDate = #10/21/2013#
MySQL
OrderDate = DATE(‘2013-10-21’)
18
Non-Graded Exercise
1. Show all Customers that comes from the City of
Altonville from Customer table
2. Show all products from Part table whose class is
AP
3. Show all Customers whose Balance is greater than
7000 from Customer table
4. Show all Customers whose Credit Limit is above or
equal to 7500 from Customer table
5. Show all Customers whose balance is less than
500 from Customer table
6. Show all orders from Orders table whose order is
beyond 10/20/2013
19
Compound Conditions
• Compound condition
– Connecting two or more simple conditions using one
or both of the following operators: AND and OR
– Preceding a single condition with the NOT operator
• Connecting simple conditions using AND operator
– All of the simple conditions must be true for the
compound condition to be true
• Connecting simple conditions using OR operator
– Any of the simple conditions must be true for the
compound condition to be true
20
AND – Truth Table
• In order for AND to be true all
conditions/expressions should be true
Condition 1
Condition 2
Result
False
False
False
False
True
False
True
False
False
True
True
True
21
AND – Truth Table (Example)
• Example : Age>20 AND State=‘Pohnpei’
Age
State
Result/Answer
20
Chuuk
False
21
Yap
False
19
Pohnpei
False
21
Pohnpei
True
22
OR – Truth Table
• In order for OR to be True at least one
conditions/expressions should be true
Condition 1
Condition 2
Result
False
False
False
False
True
True
True
False
True
True
True
True
23
OR – Truth Table (Example)
• Example : Age>20 OR State=‘Pohnpei’
Age
State
Result/Answer
20
Chuuk
False
21
Yap
True
19
Pohnpei
True
21
Pohnpei
True
24
Compound Conditions (continued)
FIGURE 3-15: Compound condition that uses the AND operator
FIGURE 3-16: Query results
25
Compound Conditions (continued)
FIGURE 3-17: Compound condition that uses the OR operator
FIGURE 3-18: Query results
26
Non-Graded Exercise
1. Show all products from Part table whose class is
AP and its price is above $400
2. Show all Customers that comes from either the City
of Fillmore or Grove from Customer table
3. Show all Customers whose Credit Limit is $7,500
but its Balance is above $5,000 from Customer
table
4. Show all products whose warehouse is from either
1 or 2
5. Show all products whose On hand quantity is
above 20 and coming from Warehouse no. 3
27
Compound Conditions (continued)
• Preceding a condition by NOT operator
– Reverses the truth or falsity of the original condition
• BETWEEN operator
– Value must be between the listed numbers
28
Compound Conditions (continued)
• Using NOT operator
– Example 1: SELECT * FROM Customer WHERE
NOT City=‘Grove’
– Example 2: SELECT * FROM Customer WHERE
NOT CreditLimit=10000
• Using BETWEEN operator
– Example 1: SELECT * FROM Customer WHERE
Balance BETWEEN 5000 AND 10000
– Example 2: SELECT * FROM Orders WHERE
Orderdate BETWEEN #10/20/2013# AND
#10/21/2013
29
Non-Graded Exercise
1. Show all products from Part whose Class is not
from AP
2. Show all products from Part whose Warehouse is
not from Warehouse number 3
3. Show all customers from Customer whose sales
representative is not Repnum no. 65
4. Show all products from Part whose Price is from
$300 to $600.
5. Show all products from Part whose On hand
quantity is from 20 to 50
30
Computed Fields
• Computed field or calculated field
– Field whose values you derive from existing fields
– Can involve:
•
•
•
•
Addition (+)
Subtraction (-)
Multiplication (*)
Division (/)
31
Computed Fields (continued)
• Numeric Computed Fields
– Example 1: Computing the Net by deducting Credit Limit from Balance
SELECT Customername, (Balance-CreditLimit) as
Net FROM Customer
– Example 2: Computing the Running Total by Multiplying On hand quantity
with Price
SELECT Partnum, Description, OnHand * Price as
RunningTotal FROM Part
• Non-numeric Computed Field
– Example 1: Concatenating or Joining Last name and First
name of the
Sales as Full Name
SELECT Repnum, Lastname + “, “ + Firstname as
Fullname FROM Rep
32
Computed Fields (continued)
FIGURE 3-25: SQL query with a computed field and condition
FIGURE 3-26: Query results
33
Non-Graded Exercise
1. Show customer name and a computed field name
Net using the formula CreditLimit – Balance from
Customer table.
2. Get the Running Total from each order by
multiplying Number Ordered and Quoted Price of
the Orderline table. Aside from the Running Total
show also the Order Number.
3. Get the Running Total per product from Part table
by multiplying Quantity on Hand by price. Show
also the Description of the product.
4. Make a concatenated field for Street, City, State
and Zip fields and named it Address, from
Customer table. Show also the Customer name
before the address.
34
Using Special Operators (LIKE and IN)
• Wildcards in Access SQL
– Asterisk (*): collection of characters
– Question mark (?): any individual character
• Wildcards in MySQL
– Percent sign (%): any collection of characters
– Underscore (_): any individual character
• To use a wildcard, include the LIKE operator in the
WHERE clause
• IN operator provides a concise way of phrasing
certain conditions
35
Using LIKE operator and wildcards
• Using asterisk for collection of characters pattern
– Example 1: Displays customer whose name starts with letter B
SELECT * FROM Customer WHERE customername LIKE ‘B*’
– Example 2: Displays customer whose name starts with the word Brook
SELECT * FROM Customer WHERE customername LIKE
‘Brook*’
• Using question mark for individual/single character
– Example 1: Display orders whose partnum starts with letter K followed by any 3
characters.
SELECT * FROM Orderline WHERE partnum LIKE ‘K???’
– Example 2: Display product whose class startswith letter A
followed by one character.
SELECT * FROM Part WHERE class LIKE ‘A?’
36
Using the IN operator
– Example 1: Displays customer whose credit limit is either $5,000 or $10,000 or
$15,000
SELECT * FROM Customer WHERE creditlimit
IN(5000,10000,15000)
– Example 2: Displays customer who comes from the City of Grove, Crystal, Fillmore
or Northfield
SELECT * FROM Customer WHERE city
IN(‘Grove’,’Crystal’,’Fillmore’,’Northfield’)
37
Non-Graded Exercise
1. Show all products from Part table that starts with
letter ‘D’
2. Show all customers from Customer table whose
Street starts with 28
3. Using IN show products whose class is AP or SG
from Part table
4. Using IN show customers whose Credit Limit is
either 5000, 10000 or 15000.
38
Sorting
• Sort data using the ORDER BY clause
• Sort key: field on which to sort data
• When sorting data on two fields:
– Major sort key (or primary sort key): more important
sort key
– Minor sort key (or secondary sort key): less
important sort key
39
Using the ORDER BY statement
– Example 1: Displays customer sorted by customer name
SELECT * FROM Customer ORDER BY customername
– Example 2: Displays sales rep sorted by Lastname then Firstname
SELECT * FROM Rep ORDER BY Lastname, Firstname
– Example 3: Displays sales rep sorted by Lastname in descending order
SELECT * FROM Rep ORDER BY Lastname DESC
– Example 4: Displays customer sorted by City whose Credit Limit is $10,000
SELECT * FROM Customer WHERE CreditLimit = 10000
ORDER BY city
40
Non-Graded Exercise
1. Show all products from Part table and sort it
according to Product name
2. Show all products from Part table and sort it
according to Warehouse and then product name
3. Show all products ordered from Orderline table
and sort it according to Number of product ordered
and in Descending order
41
Built-in Functions
• Built-in functions (aggregate functions) in SQL
– COUNT: calculates number of entries
– SUM or AVG: calculates sum or average of all
entries in a given column
– MAX or MIN: calculates largest or smallest values
respectively
42
Using Aggregate Functions (COUNT,
SUM, AVG, MAX, MIN)
– Example 1: Count all how many customers in Customer table
SELECT COUNT(*) as CustomerCount FROM Customer
– Example 2: Count how many customers from the City of Grove
SELECT COUNT(*) as CountGrove FROM Customer
WHERE city = ‘Grove’
– Example 3: Sum all Balance from all Customers
SELECT SUM(Balance) as TotalBalance FROM Customer
– Example 4: Sum all Balance from all Customers for those who a CreditLimit of
$5,000
SELECT SUM(Balance) as TotalBalance FROM Customer
WHERE CreditLimit=5000
43
Non-Graded Exercise
1. Count all the products from Part table
2. Count all the products from Part table whose Class
is either ‘AP’ or ‘SG’
3. Give the Total for the Quantity On Hand from Part
table
4. Give the Sum or Total for the Quoted Price from
Orderline table
5. Give the Sum or Total for the Quoted Price from
Orderline table whose Quoted Price is above $400
44
Subqueries
• Subquery: inner query
• Subquery is evaluated first
• Outer query is evaluated after the subquery
45
Using Subquery
– Example 1: Select orders where whose parts/products are from Warehouse No. 3
SELECT Ordernum FROM Orderline WHERE Partnum IN
(SELECT Partnum FROM Part WHERE Warehouse = ‘3’)
46
Grouping
• Create groups of records that share a common
characteristic
• GROUP BY clause indicates grouping in SQL
• HAVING clause is to groups what the WHERE
clause is to rows
47
Using GROUP BY
– Example 1: Count how many customers per Sales Representative
SELECT Repnum, COUNT(*) as TotalCustomersPerRep
FROM Customer GROUP BY Repnum
– Example 2: Get the Total of how much Quantity on Hand per Class of all the products
SELECT Class, SUM(OnHand) as TotalPerClass
FROM Part GROUP BY Class
48
Using HAVING
– Example 2: Get the Total of how much Quantity on Hand per Class of all products
that have Quantity on hand above 70
SELECT Class, SUM(OnHand) as TotalPerClass
FROM Part GROUP BY Class HAVING SUM(OnHand) > 70
49
Non-Graded Exercise
1. Using subquery show orders from Orderline table
that has a class of ‘AP’ in Part table
2. Count all customers from Customer table per City.
3. Sum all Quantity on Hand from Part table per
Warehouse Number.
4. Display the Sum of Quantity on Hand from Part
table per Warehouse Number that has Total
Quantity on hand above 100.
50
Joining Tables
•
•
•
Queries can locate data from more than one table
Enter appropriate conditions in the WHERE clause
To join tables, construct the SQL command as:
1. SELECT clause: list all fields you want to display
2. FROM clause: list all tables involved in the query
3. WHERE clause: give the condition that will restrict
the data to be retrieved to only those rows from the
two tables that match
4. Or you could use INNER JOIN in same manner as
no. 3
51
Joining tables example
– Example 1: Joining tables using WHERE clause
SELECT CustomerNum, CustomerName, Rep.Repnum,
Lastname, Firstname FROM Customer, Rep
WHERE Customer.Repnum = Rep.Repnum
– Example 2: Joining tables using INNER JOIN
SELECT A.CustomerNum, A.CustomerName, B.Repnum,
B.Lastname, B.Firstname FROM Customer A INNER JOIN
Rep B ON A.Repnum = B.Repnum
52
Non-Graded Exercise
1. Using WHERE clause join Orderline and Part
tables showing Ordernum from Orderline table
then Partnum and Description from Part table
2. Using INNER JOIN, join Orderline and Part tables
showing Ordernum from Orderline table then
Partnum and Description from Part table
53
Updating Tables
• UPDATE command makes changes to existing data
• INSERT command adds new data to a table
• DELETE command deletes data from the database
54
Updating Table using UPDATE command
– Example 1: Updating one field
UPDATE Customer SET City=‘Manila’ WHERE
Customernum=‘524’
– Example 2: Updating more than one field
UPDATE Rep SET Lastname=‘Doe’, Firstname=‘John’
WHERE Repnum=‘65’
– Example 3: Updating involving computation
UPDATE Part SET OnHand=OnHand-1 WHERE
Warehouse=‘2’
55
Non-Graded Exercise
1. Using update command from Customer table
restore back the City of Customer name Kline’s
from Manila to Fillmore
2. Using update command from Rep table restore
back the Firstname and Lastname of Sales Rep
John Doe to Juan Perez
3. Using update command restore back from Part
table to OnHand quantity plus 1 this time whose
Warehouse is ‘2’
4. Using update command from Part change the
Class name to ‘HH’ whose class name is ‘HW’
5. Using update Change all the City of Rep table to
Ponpei and Rate to 0.08
56
Updating Table using INSERT command
– Example 1: Inserting a record involving all fields
INSERT INTO Part VALUES ('RC24','Rice
Cooker',100,'AP','3',75.50)
– Example 2: Inserting a record involving specific fields
INSERT INTO Part (Partnum, Description,Class,Price)
VALUES ('PL10','Power Lifts','SG',250.00)
57
Creating a Table from a Query
• INTO clause
– Saves the results of a query as a table
– Specified before FROM and WHERE clauses
• MySQL
– Create the new table using a CREATE TABLE
command
– Use an INSERT command to insert the appropriate
data into the new table
58
Creating a Table from a Query
(continued)
FIGURE 3-60a: Query to create a new table (Access)
59
Creating a Table from a Query
(continued)
FIGURE 3-60b: Query to create a new table (for Oracle and MySQL)
60
Summary of SQL Commands
• Generic versions of SQL commands for every
example presented in this chapter
• In most cases, commands in Access are identical
to the generic versions
• For those commands that differ, both the generic
version and the Access version are included
61
Summary
• Structured Query Language (SQL) is a language
that is used to manipulate relational databases
• Basic form of an SQL query: SELECT-FROMWHERE
• Use CREATE TABLE command to describe table
layout to the DBMS, which creates the table
• In SQL retrieval commands, fields are listed after
SELECT, tables are listed after FROM, and
conditions are listed after WHERE
• In conditions, character values must be enclosed in
single quotation marks
62
Summary (continued)
• Compound conditions are formed by combining
simple conditions using either or both of the
following operators: AND and OR
• Sorting is accomplished using ORDER BY clause
• When the data is sorted in more than one field, can
have a major and minor sort key
• Grouping: use the GROUP BY clause
• HAVING clause: restricts the rows to be displayed
63
Summary (continued)
• Joining tables: use a condition that relates
matching rows in the tables to be joined
• Built-in (aggregate) functions: COUNT, SUM, AVG,
MAX, and MIN
• One SQL query can be placed inside another; the
subquery is evaluated first
• UNION operator: unifies the results of two queries
64
Summary (continued)
• Calculated fields: include the calculation, the word
AS, the name of the calculated field
• INSERT command adds a new row to a table
• UPDATE command changes existing data
• DELETE command deletes records
• INTO clause is used in a SELECT command to
create a table containing the results of the query
65